In order to secure increase flexibility, data processing systems have migrated to LAN (Local Area Network) communication systems so that individual computer workstations can be connected to data servers, printers, and other facilities. Up until recently, most of these LAN systems have been wired so that when a user wished to connect to the LAN the user must secure a physical or wired connection to the LAN in order to participate in communications on the LAN.
In order to secure a more flexible system to dispense with wiring and permit a flexible arrangement in which workstations or other devices (which we will collectively call nodes), could be added to or removed from wireless LANs were developed. The most convenient way that has been found to operate successfully is by means of light communication, particularly using infrared wavelengths of light, to communicate between the various nodes in an infrared LAN system.
As is well known in the art at the present time, each of the nodes in such a LAN system would have associated with it (and likely built into it) an infrared transceiver, typically complying with the IrDA Association standards. This transceiver typically achieves communications by using an LED (Light Emitting Diode as an infrared emitter). In accordance with the standards of the IrDA Association, the pattern of infrared light emitted is typically in the form of a cone of light of about 60° angle. This provides effective communication over a short range with relatively low sensitivity to the positioning of the direction of the transceiver, emitter or receiving device. However, as will be well recognized, the range of communications is limited by the amount of power which can be emitted by the emitter. As this light is spread out as it is emitted, the power density available at a given distance will follow the inverse square law. This limits the distance over which data transmission can occur as the power density will fall off beyond the density required for effective transmission when communicating nodes are separated by excessive distance.
If increased range is desired, the amount of light energy emitted by the LED could possibly be increased; however, this will be limited by the nature of the LED employed and by maximum safe limitations imposed by government or safety regulations to protect users from excessive exposure to infrared light
Alternatively, it is possible to extend the range of a transceiver by collimating or focusing the light to constrain it into a narrow beam. However devices which use light for communication are constrained by the requirement that each node of the system included in the LAN must be in the light path involved. This would typically preclude more than two devices from communicating using a collimated beam unless all devices or nodes in the LAN were lined up with the beam or a mirror system was used to reflect the beams used to the different nodes, all of which is unnecessarily complex for simple operation.
Accordingly, in order to achieve the advantages of both a divergent pattern of infrared light transmission which would permit significant flexibility in the arrangement of nodes in the LAN and also to make available the use of collimated light for longer distant communications it would be desirable to have a system or device which would be capable of operating in both of these modes presenting the capabilities of switching from a collimated to a non-collimated mode as required.
The present invention provides a simple, efficient system in which a transceiver is provided that has a dual mode of operation; collimated, and non-collimated.